Total Solutions for Exosomes

Exosomes are small membrane-bound vesicles with a lipid bilayer structure, secreted by most cell types within the body. Their diameter typically ranges from approximately 30 to 150 nm.

Exosomes are actively secreted by most living cells through the process of exocytosis and are found in body fluids such as plasma, urine, serum, saliva, and cerebrospinal fluid (CSF).

With a lipid bilayer structure, exosomes carry characteristic transmembrane proteins and receptors, adhesion molecules, lipid raft-associated proteins, and immunomodulatory molecules. Within the lumen of exosomes, a variety of proteins and nucleic acids can be detected, varying depending on the cell type of origin.

As key mediators of intercellular communication, exosomes deliver bioactive molecules to recipient cells, thereby participating in a wide range of pathophysiological processes, including tumorigenesis, cardiovascular diseases, and neurodegenerative disorders.

Exosome Structure [1]

Image source: Fujita Y. et al., 2015 [1]

In recent years, with advancements in technology and experimental discoveries by researchers, exosomes have been shown to be applicable in early cancer detection, prognosis, and therapeutic guidance. Additionally, due to their natural nanoparticle properties and structural stability, exosomes hold potential as carriers for the development of targeted drug delivery systems.

The application of exosomes requires distinguishing them from other extracellular vesicle populations, such as microvesicles (which bud from the plasma membrane and are also referred to as ectosomes or shedding vesicles) and apoptotic bodies. With technological progress, numerous methods for exosome isolation have been developed, each with its own advantages and limitations.

Common Exosome Isolation Methods

• Immunoaffinity Separation: This method separates exosomes by the specific binding of antibodies to surface protein markers. The advantages are high purity, high specificity, and no impact on exosome morphology. It is suitable for the qualitative and quantitative analysis of exosomal proteins. The main drawback is its inability to handle large-scale sample production, and it may require pre-enrichment, resulting in low yield.

• Ultracentrifugation: As the name suggests, this method uses an ultracentrifuge to separate particles based on differences in size, density, etc. The advantage is a high recovery rate. However, the drawbacks include the need for an ultracentrifuge (which is costly), the risk of exosome damage due to the high centrifugal force, and the time-consuming nature of the process. It is not suitable for large-scale production, and the purity is lower when separating from viscous samples.

• Polymer Precipitation: This method uses polymers (such as PEG) to competitively bind with free water molecules, causing the exosomes to precipitate, which are then recovered by centrifugation. The advantages include minimal damage to exosomes, use of neutral pH, simple operation, and high recovery rate. The disadvantages are lower purity, higher impurity levels, the inability to scale up the centrifugation process, higher costs, and longer processing time.

• Ultrafiltration: This method uses ultrafiltration to separate exosomes. The advantage is the simplicity and speed of the process. The main disadvantages are a low recovery rate, as exosomes may adhere to the ultrafiltration membrane, leading to a loss in yield. Additionally, exosomes are sensitive to shear forces, and unstable control of pressure and shear forces may cause exosome deformation, thereby affecting their integrity.

• Chromatography: This method separates exosomes based on their particle size using specific packing materials. The advantages are high purity, high yield, scalability, and reproducibility of the process. Increasingly, researchers are opting for chromatography using packing materials to separate and purify exosomes, achieving high-purity samples.

BioLink offers end-to-end solutions for exosome purification. For upstream cell culture, small-scale production can utilize the CytoLinX® WB Single-use Rocking Bioreactor, while large-scale production can employ the CytoLinX® BR Single-use Bioreactor. These options cater to various production scales, ensuring flexibility and efficiency.

CytoLinX® WB Single-use Rocking Bioreactor

CytoLinX® WB Single-use Rocking Bioreactor

• The software provides a user-friendly interface with stable and reliable control, ensuring compliance with 21 CFR Part 11 regulations.

• Optional modules include pH, DO, and perfusion systems, allowing customization to meet specific application needs.

• Gas flow is precisely measured using a mass flow controller (MFC), ensuring accurate and reliable regulation.

• The consumables are available in a variety of designs, including basic models, models equipped with pH and DO electrodes, and perfusion models.

• The single-use consumables are designed to encompass cell therapy systems.

CytoLinX® BR Single-use Bioreactor

CytoLinX® BR Single-use Bioreactor

Hardware Flexibility and Robustness:

• The flexibility of the PCS 7 control system complies with the design and specifications of the ISA 88 batch control system, enabling the implementation of batch functions.

• It allows for plant-wide batch control, supports hot-swappable controllers, and can connect to multiple reactors. It is not limited to controlling only BioLink tanks.

• The stability of equipment control is exceptional, with excellent interactivity between temperature, pH, and DO.

Consumable Safety and Variety:

• There is a wide range of consumable options, including micro, medium, and macro spargers, catering to different process needs.

• Imported gas filters ensure the integrity of the bags.

Downstream purification solutions can be tailored to different routes based on process requirements, BioLink’s multimodal resins exhibit better performance and applications in exosomes.

The BioLink MaXtar® COLL series multimodal resin features a dual-layer structure. Its shell is composed of a porous passivation layer, while the core is a spherical interior functionalized with ligands exhibiting both hydrophobic interaction and anionic adsorption properties. This design optimizes the removal of impurities such as host proteins and nucleic acids. The MaXtar® COLL series includes:

• MaXtar® COLL 400 (ensures that molecules larger than 400 kDa do not enter the pores and flow directly through the outer water stream),

• MaXtar® COLL 700 (ensures that molecules larger than 700 kDa do not enter the pores and flow directly through the outer water stream).

MaXtar® COLL dual-layer structure

Compared to traditional single-mode chromatography resin, the MaXtar® COLL series demonstrates superior performance:

• The unique dual-layer structure allows flow-through processing of macromolecules, simplifying process optimization and enabling easier linear scalability.

• The improved MaXtar® matrix features enhanced rigidity, allowing higher process flow rates at lower back pressure, thereby increasing process efficiency.

• Compared to traditional gel filtration chromatography, the MaXtar® COLL series offers a significantly higher sample loading capacity, resulting in reduced costs.

The MaXtar® COLL series multimodal chromatography resin from BioLink demonstrate excellent performance in exosome separation. Based on the analysis of collected samples during customer testing, it has been confirmed that the separation objectives for this project can be achieved. Further optimization of the conditions is currently underway.

COLL700, flow-through mode (blue)

COLL400, flow-through mode (orange)

In addition, hollow fibers are increasingly being used, both for upstream clarification harvests and downstream separation and purification. Different pore sizes of hollow fibers are selected depending on the desired end result to achieve higher purity products. The TFFNOVA® Hollow Fiber Filter provided by BioLink are widely used in the vaccine industry, and in the exosome industry, hollow fibers can also be used for purification or collection depending on the final objective.

TFFNOVA Hollow Filber Filter and FiltraLinX® Benchtop Semi-automatic TFF System

The TFFNOVA® Hollow Fiber Filter provided by BioLink are developed and manufactured under the ISO 9001:2015 Quality Management System. Each filter undergoes strict quality inspection and is shipped with a quality assurance certificate.

• Biocompatibility: All flow path materials meet the USP <88> Class VI biocompatibility standard;

• Microbial limits: < 1000 CFU/unit;

• Endotoxins: < 0.25 EU/ml;

• No animal-derived materials: The raw materials used in the filters do not contain any animal-derived ingredients or derivatives.

• Transport and packaging validation: Compliant with ISTA 3A (2008) requirements.

Exosomes, as an emerging class of therapeutics, are also being applied in clinical research. While smaller samples for research can be obtained using different methods, the production of commercial or clinical phase II and III samples will require stable processes and regulatory-compliant production workflows. Purification methods will increasingly be applied in the industry.